1. Field of the Invention
This invention relates in general to the fabrication of a magnetic recording medium, and more particularly, to a modified magnetic recording medium with light textured surface by using a two-step light texturing process before forming the laser texture on a disk substrate. Pluralities of circumferential light textures are formed on a disk substrate to improve the properties of the laser textured landing zone and the magnetic layer.
2. Description of Related Art
A hard-disk drive is a data storage device that contains at least one magnetic recording medium. It has been widely utilized in today's electrical information industry. A hard-disk drive essentially includes: a rotatable disk with concentric data tracks containing the information; a head for reading and/or writing data; and an actuator connected to a carrier for moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator, and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
FIG. 1 depicts a plan view of a conventional magnetic recording medium and a head for reading and/or writing operations, schematically illustrating the basic configuration and structural relationship of a hard-disk drive. As shown in the drawing, there is a disk substrate 20, such as an aluminum (Al) disk plated with nickel-phosphorous (NiP). The center area of the disk substrate 20 is engaged with a rotatable spindle (not shown). An annular area adjacent to the outer edge 202 of the disk substrate 20 is coated with a magnetic layer to form an annular data region 21. A head 27 is disposed on a carrier 24 and an actuator 26 connected to the carrier 24 for moving the head 27 to the desired track. Another annular area adjacent to the inner edge 201 of the disk substrate 20 is textured to form a landing zone 23. In conventional magnetic hard-disk drive, the head carrier is an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed.
To improve the wear resistance of the disk substrate 20, as well as to maintain consistent magnetic properties, it is desirable to make the disk surface as smooth as possible. However, a very smooth disk surface creates a problem known as "stiction." This means that after the slider has been in stationary contact with the disk for a period of time, the slider tends to resist translational movement or "stick" to the disk surface. Stiction in a hard disk drive can result in damage to the head 27 or disk substrate 20 when the slider suddenly breaks free from the disk surface when disk rotation is initiated. In some hard-disk drives, such as low-power hard-disk drives used in laptop and notebook computers, the disk drive motor may simply be unable to initiate rotation or achieve operating speed because of the adhesion forces that cause stuck sliders or excessive drag.
It is noted that the head 27 comes into contact with the disk substrate 20 only when it lands on the landing zone 23. Thus, in order to prevent the stiction problem, a plurality of texture are usually formed on the landing zone 23 to increase the surface roughness, thereby reducing the stiction between the head 27 and the disk substrate 20. The U.S. Pat. No. 5,109,781 and No. 5,062,021 disclose a method of forming texture on the landing zone using a laser-texturing process. FIG. 2 is a flow chart showing the above laser texturing process of fabricating a magnetic recording medium. Starting with step 10 of the flow chart, a disk substrate, such as an aluminum disk plated with nickel-phosphorous is provided. Next, going on to step 12 of the flow chart, a mechanical polishing process is performed to produce a substantially even surface on the disk substrate. Then, going on to step 14 of the flow chart, a plurality of textures are created on the inner portion of the disk substrate by laser pulse to form an annular landing zone. After that, going to steps 16 and 18 of the flow chart, a magnetic layer and a protective layer are successively formed on the surface of the disk substrate.
Accordingly, the disk drive properties can be improved by forming a laser texture on the landing zone to reduce disk stiction. However, as the surface roughness of the disk substrates from various supplier differs, abnormal asperity usually remains on the surface of the disk substrates, even after performing the mechanical polishing process. Further, as the amount of exposure time in the air increases, an oxide film is inevitably formed on the surface of the disk substrate. This not only affects the surface roughness of the disk substrate but also varies the surface composition of the disk substrate. When applying the laser pulse to these various materials, the results are unpredictable.
FIG. 3 is a partial perspective view of the magnetic recording medium fabricated by the process of FIG. 2. Several abnormal asperities are found on the surface of the disk substrate. These degrade the surface smoothness of the disk substrate, resulting in poor control of the size and structure of the laser texture. In addition, as shown in FIG. 3, with irregular distribution of the mechanical polished texture on the disk substrate, some main properties of the latter-formed magnetic layer, such as the coercivity (Hcr) and the remanence (Mrt) exceed the desired range.